docs: def payment_status_changed_listener(sender, instance, old_status, new_status, **kwargs):
      """
      Here we will actually do something, when payment is accepted.
      E.g. lets change an order status.
      """
      logger.debug("payment_status_changed_listener, old=%s, new=%s", old_status,
                   new_status)
      if old_status != 'paid' and new_status == 'paid':
          # Ensures that we process order only one
          instance.order.status = 'P'
          instance.order.save()